http: remove unneeded cb check from setTimeout

- check is already covered by event emitter

Author: aks-

lib/_http_outgoing.js

@@ -91,8 +91,6 @@ exports.OutgoingMessage = OutgoingMessage;
 OutgoingMessage.prototype.setTimeout = function(msecs, callback) {
 
   if (callback) {
-    if (typeof callback !== 'function')
-      throw new TypeError('callback must be a function');
     this.on('timeout', callback);
   }